HONOLULU -- Two civilian shipyard workers at Joint Base Pearl Harbor-Hickam in Honolulu were killed by a US sailor on Wednesday, Rear Adm. Robert Chadwick told reporters.
The shooter then killed himself, Chadwick said.
A third civilian employee was wounded and is stable at a hospital, Chadwick added.
US Navy Cmdr. Lydia Robertson said the sailor took their life after opening fire near Shipyard Drydock 2, a maintenance area for nuclear submarines.
Authorities have not released the sailor's identity.
The incident occurred at 2:30 p.m. HST (7:30 p.m. ET) at the Pearl Harbor Naval shipyard, officials tweeted on the base's verified Twitter account.
About three hours later, Robertson said the scene was secured and the base had reopened. Both base security and Navy Investigative Services are conducting the investigation, she said.
Several witnesses told KGMB/KHNL that they heard gunshots.
The Queen's Medical Center in Honolulu received one patient from the incident, Minna Sugimoto, a spokeswoman for The Queen's Health System, told CNN.
There were no other details about the victims.
The shooting occurred three days before commemorations of the Japanese attack that thrust the United States into World War II.
The base houses Air Force and Navy units and the base population, as of 2015, was more than 66,000.